Active Noise Cancellation

1. Active Noise Cancellation Dr. Farrukh   Department of Electrical & Electronics Engineering, College of Engineering, University Tenaga Nasional, Jalan Kajang-Puchong, 43009 Kajang, Selangor, MALAYSIA. Farrukh@uniten.edu.my

2. Description of paper • Use of TMS320C5402 DSK-single TMS320C6701 EVM – dual channel channel Active Noise Cancellation in duct system • Uses feedback + feedforward topology -designed to cancel narrowband periodic tones.

3. Problem Description!!!! What is Noise ????? • Unwanted sound that • is often loud and irritating • Industrial equipment • Damaging to human from both • a physical and psychological aspect Reason Active Noise Cancellation???

4. How does Active Noise Cancellation (ANC) works ? • Identical and in phase • Volumes increases • Basic principles by introducing a canceling anti-noise signal that has the same amplitude but the exact opposite phase and resulting a reduction noise signal • Out of phase • Volumes decreases Active noise cancellation

5. Hardware Approaches of ANC • Feedforward Topology • Reference noise and • cancelled noise are used • 2 inputs and 1 output • Feedback Topology • only cancelled noise • are used – one input and one output • Use of TMS320C5402 DSK-single • channel Active Noise Cancellation • in duct system

6. Hardware Secondary Path,S(z) Estimate Secondary Path,S^(z) Feedback Topology x(n) e(n) • to estimate primary noise and use it as a reference X(z)= E(z) + S(z)Y(z) Duct system y(n) • Need to estimate the secondary path transfer function W(z) S^(z) L MS y(n) x^(n) DSP System

7. Hardware Canceling zone microphone Input noise Canceling loudspeaker Amplifier Feedback Experimental Setup-ANC Noise loudspeaker S(z) x(n) e(n) Amplifier Secondary Path IN OUT y(n) LMS Algorithm DSP TMS320C5402 DSK

8. Feedforward Topology x(n) • Coherent input is captured, filtered and feed into LMS d(n) e(n) Primary function, P(z) y’(n) Secondary Path,S(z) Duct system • Estimation of the secondary path transfer function is obtained by identification process y(n) W(z) Estimation of S(z), Ŝ(z) LMS e(n) x^(n) DSP System

9. Hardware Feedforward Experimental Setup Canceling zone Noise speaker microphone x(n) S(z) e(n) Secondary Path Input noise y(n) Canceling speaker Amplifier TMS320C6701 EVM DSP

10. Software • Update the weights • The error • The output Least Mean Square (LMS) Algorithm

11. microphone S(z) Canceling loudspeaker Amplifier LMS Algorithm Secondary path S(z) duct modeling Result of identification of the secondary path

12. Single channel cancellation results Input Frequency =120Hz

13. Input Frequency = 70 + 80 Hz Without cancellation With cancellation

14. Cancellation result on 70+80+100+110+120+130Hz

15. Dual Channel cancellation Results Input Frequency =80Hz No cancellation With cancellation

16. Input Frequency = 40+70Hz no cancellation cancellation

17. no cancellation cancellation Cancellation result on 40 + 70 + 80Hz

18. Conclusions • ANC was first time attempted in Malaysia and obtained compatible results. • Integrated programming of DSP was achieved without any external aid or training. • This work yields Masters thesis and research papers accepted by local and international conferences. • The expertise developed is now being shared with other groups, projects and laboratory work in COE.

19. Future Scope • Acoustic wave propagation in duct boundary is investigated with PDE –Finite Element method will be the future direction • Boundary value conditions at the exhaust of duct can be studied with FEM • Build dedicated DSP hardware for embedded standalone ANC system • PCB for audio amplifiers and speakers are needed for mobility of test rig

20. FINITE ELEMENT METHOD – ANALYSIS OF DUCT SYSTEM

21. ACCOUSTIC ENERGY INSIDE THE DUCT

22. The end